Tire pressure

[tagger_99]

New Guy here, well been reading for a while, first post.
In early March we bought a 2015 Thor Freedom Elite 23H with 10500 miles on it, closed on our home in Indianapolis,In mid March and been living in the RV since then (retired).
Staying in Fort Myers, Fl at this time learning the ropes.

Tire pressure,

have not weighed the rig yet, plan on going to CAT scale tomorrow.

With the information on the driver door:

GVWR 12500lb

GAWR
Front:4600 LT225/75R16E Cold inflation pressure 75 PSI Single
Rear:8500 LT225/75R16E Cold inflation pressure 65 PSI Dual

And the information on the tire:
max load single
2680lb 80psi cold
max load dual
2470lb 80psi cold

Until I weigh the beast I'm running
80psi cold front
70psi cold rear

Does this seem reasonable ?
Thanks for the input.

[rskrbina]

Your right on track. I'm always in a hurry to get the weight ticket in hand and start adjusting. Have fun!!

[Chance]

Originally Posted by tagger_99

....cut....

Does this seem reasonable ?
Thanks for the input.

Congratulations on your retirement.

As to tire pressure, I'm not sure it's necessary (or reasonable?) to go over the listed pressure on placard. The listed pressure (unless there has been an error) is based on tires being able to handle the maximum axle weight ratings, so why go higher?

In your case, the 80 PSI you are using in front can handle 5,360 pounds, which is much higher than the maximum 4,600 pounds the front axle is set up to handle. So unless you plan to run way overloaded, why use 80 PSI?

You'll know better when you get an actual weight, but for the most part I don't believe it's necessary to run higher pressures than indicated on placard.

More often than not, a case can be made to run tire pressures lower on lightly-loaded motorhomes. I know a few who run higher pressures to save fuel (lowers rolling resistance), but I personally don't think it's worth the harsher ride that comes with overinflated tires. Too much pressure can also reduce tire traction capability.

[tagger_99]

OK

I will load up in the morning, add two cans of Seafoam to the fuel tank, Dawn dish soap and Calgon to a 3/4 full black water tank, start the generator and drive for 40 or so miles weigh it and return with my results.
Thanks for the suggestions.

Tom

[Travelin' Texans]

On your way that 40 miles, it sounds reasonable to me to run 80 psi cold in the front & 70 psi cold in the rear & after weighing on your way back I'd run 80 psi cold in the front & 70 psi cold in the rear, then once you burn the Seafoam & dump the black water I'd run 80 psi cold in the front & 70 psi cold in the rear.

[KNMIB]

Right on Texan

[Oneilkeys]

Unless you think or know that you are at max weight for the axel, I am not sure why you want to run your tires at max pressure. Starting at 80 psi cold, you may be running them at 86 psi on the interstate. While the tires are obviously designed to do that, I don't see the need or the sense to stress them at max pressure all the time if you do not need to? Maybe I am missing something?

[Chance]

Originally Posted by Oneilkeys

....cut.... Maybe I am missing something?

I must be missing something also.

[tagger_99]

Well here are the three numbers from the CAT Scale this morning.

steer axle: 3680lb
drive axle: 7340
gross weight: 11020

I have been looking at this site,
Michelin RV Tires | View Michelin RV Tires load and inflation tables for motorhomes and recreational vehicles. | Michelin RV Tires
but I don't have it figured out yet
Tires are, LT225/75 MichelinR16

I have ordered an American Car Dolly which should be here in 3 or 4 weeks
to pull a 2013 Fiat 500, that weighs around 2300 lb.

any help appreciated on interpreting these numbers.

Tom

[Chance]

Originally Posted by tagger_99

Well here are the three numbers from the CAT Scale this morning.

steer axle: 3680lb
drive axle: 7340
gross weight: 11020

I have been looking at this site,
Michelin RV Tires | View Michelin RV Tires load and inflation tables for motorhomes and recreational vehicles. | Michelin RV Tires
but I don't have it figured out yet
Tires are, LT225/75 MichelinR16

I have ordered an American Car Dolly which should be here in 3 or 4 weeks
to pull a 2013 Fiat 500, that weighs around 2300 lb.

any help appreciated on interpreting these numbers.

Tom

Tom, that's good data. Was the motorhome fully loaded as you would drive it?

Also, what are you trying to figure out? In other words, what exactly are you trying to accomplish? Are you trying to soften ride, improve MPG, change handling, or what? If you only need help understanding how the table works, let us know. I can try walking you through it.

The factory recommended pressures are plenty for your load, so I'd use that as a starting point to determine what you may want to change.

[tagger_99]

I'M really trying to understand the tables and how to use them.

So the steer axle is 3680 divided by 2 = 1840 so 45 or 50 psi according to the chart ?
Drive axle 7340 divided by 2 = 3670 so 50 or 55 psi ?

seems low to me.

[Chance]

Originally Posted by tagger_99

I'M really trying to understand the tables and how to use them.

So the steer axle is 3680 divided by 2 = 1840 so 45 or 50 psi according to the chart ?
Drive axle 7340 divided by 2 = 3670 so 50 or 55 psi ?

seems low to me.

Well, it appears you are reading table correctly.

So the question is to what end do you want to change air pressure?

The table is for "minimum" pressure, but you can go higher if you want to lower rolling resistance (which in turn makes ride harsher), or to improve handling, etc...

On my van with larger tires I could run 40 PSI front and rear according to table, but instead run 55 PSI front and 60 PSI back. Much less than that seems low, plus makes the van drive a little too loose.

If it were me, I'd start at factory pressures on placard and then wouldn't drop it too much from that.

[tagger_99]

Originally Posted by Chance

Well, it appears you are reading table correctly.

So the question is to what end do you want to change air pressure?

The table is for "minimum" pressure, but you can go higher if you want to lower rolling resistance (which in turn makes ride harsher), or to improve handling, etc...

On my van with larger tires I could run 40 PSI front and rear according to table, but instead run 55 PSI front and 60 PSI back. Much less than that seems low, plus makes the van drive a little too loose.

If it were me, I'd start at factory pressures on placard and then wouldn't drop it too much from that.

Well good to know I'm reading the chart correctly, there sure is a lot of room between the low and high end of the PSI range, not an exact science I guess.
Lower rolling resistance and better fuel mileage, handling all those are something to shoot for in my book.
My tire pressures according to the tire monitor after things had warmed up this morning were fronts 78psi rear 73 psi, I like the way it drives, so I guess I'm in the ball park.
Chance and all the others that contributed to my learning experience, I thank you !

[Chance]

Thanks for posting the data. I'm glad to see a motorhome your size can be kept around 11,000 pounds.

[Oneilkeys]

Originally Posted by tagger_99

Well good to know I'm reading the chart correctly, there sure is a lot of room between the low and high end of the PSI range, not an exact science I guess.
Lower rolling resistance and better fuel mileage, handling all those are something to shoot for in my book.
My tire pressures according to the tire monitor after things had warmed up this morning were fronts 78psi rear 73 psi, I like the way it drives, so I guess I'm in the ball park.
Chance and all the others that contributed to my learning experience, I thank you !

Remember, those Michelin figures are for cold tire pressures, not after you have run them. Hot tires will be significantly higher.